1. Field of the Invention
This invention pertains to arc welding, and more particularly to apparatus for assembling a wire welding gun.
2. Description of the Prior Art
Arc welding requires that an inert shielding gas surround the welding arc. The shielding gas is supplied to a welding gun and flows out the gun through a nozzle. The nozzle commonly surrounds a welding wire and directs the gas to the region of the workpiece being welded. Consequently, the nozzle is an important part of a wire welding gun.
To properly perform its function, the welding gun nozzle must be durable and convenient to remove, reinstall, and adjust on the gun. The nozzle must also be adequately insulated from current-carrying components of the welding gun. It is also important that the nozzle not attract weld spatter.
It is known to provide a slip-fit connection between a welding gun nozzle and a nozzle insulator or other component of the gun. Specifically, spring rings have been used that are intended to simultaneously grip the nozzle inner diameter while locked in a groove in the insulator. The prior spring rings are typically round rings made of wires having circular cross sections. Looking at FIGS. 1 and 2, relevant portions of a typical prior wire welding gun 1 are shown that pertain to a slip-fit assembly of an insulator 4 and a nozzle 3. A contact tip adapter 2 may secure the insulator 4 to a gun tube 6 of a welding gun handle, not shown, in well known manner. A welding contact tip 10 is threaded into the contact tip adapter 2. A welding wire 12 passes through the welding gun body, not shown, and eventually through the welding contact tip 10.
The insulator 4 is manufactured with two or more spaced apart circumferential grooves 5. In each groove 5 is a round spring ring 7. The spring rings 7 are cut, as at reference numeral 8, to enable them to be assembled into the insulator grooves 5. If there were no radial clearances between the spring rings 7, adapter grooves 5, and nozzle inner diameter 11, a gripping force would be set up simultaneously between the spring rings 7, the groove roots 15, and the nozzle inner diameter 11.
In actuality, however, clearances between the insulator 4, spring rings 7, and nozzle 3 are necessary to provide the required freedom of movement of the spring rings, and to allow for the tolerances inherent in the manufacture of the three components. Consequently, the width of the grooves 5 is slightly greater than the diameter of the wire from which the spring rings 7 are formed. The depth of the grooves is chosen to adequately clear the spring ring inside diameter. Therefore, a radial clearance exists between the spring rings 7 and the roots 15 of the grooves 5. Similarly, an axial clearance exists between the spring rings 7 and the sides 16 of the grooves. Axial play, i.e., motion in the directions of arrow 13, of the nozzle 3 relative to the insulator 4 is determined by the axial clearance between the spring rings and the sides 16 of the insulator grooves. Radial play of the nozzle relative to the insulator is determined by the radial clearances between the nozzle inner diameter 11 and the insulator outer diameter 9, and by the radial clearances between the spring rings and the adapter groove roots 15. Such radial and axial clearances can then combine to undersirably cause a loosened fit between the nozzle and the insulator. Further, because of the relatively long overhang of the nozzle orifice 17 from the spring rings 7, any radial clearance between the spring rings, nozzle inner diameter 11, and insulator grooves 5 is magnified at the nozzle orifice 17. Accordingly, it is highly desirable that the clearances associated with the spring rings be minimized in order to keep wobble at the nozzle orifice 17 within acceptable limits. However, machining tolerances tight enough to eliminate nozzle wobble normally render the insulator and nozzle undesirably expensive.
Thus, a need exists for improvements in the design of wire welding guns.